Computer systems are made up of Hardware, Software, and Applications. Hardware refers to the physical components of a computer, such as the monitor, keyboard, mouse, hard drive and system board. Software refers to the set of instructions that directs the hardware to accomplish a task. The best known example of software is a computer's operating system, which provides a way for the user to interact with the hardware. Software uses hardware to perform four basic functions: input, processing, storage, and output. An application is specialized software that performs a certain function, such as word processing or media reproduction.